Production method for film laminate

ABSTRACT

Provided is a production method for a film laminate by which a tough film can be bonded to a brittle film while the breakage of the brittle film is prevented. The production method for a film laminate of the present invention includes bonding a tough film having an elongated shape to a brittle film having an elongated shape while conveying the brittle film, wherein the method includes bonding the tough film and the brittle film to each other by bringing the tough film close to the brittle film, followed by blowing of a gas from a side of the tough film opposite to the brittle film.

TECHNICAL FIELD

The present invention relates to a production method for a film laminateincluding a brittle film and a tough film.

BACKGROUND ART

A glass material, a composite containing the glass material, or the likehas heretofore been used in a member forming an image display apparatus,such as a substrate for a display element, a sealing material for anOLED element, or a front protective sheet. In addition, in recent years,the weight saving and thinning of the image display apparatus have beenprogressing, and hence the use of a thinner glass material has beenrequired. The glass material originally involves a problem in that itshandleability is poor owing to its brittleness, and along with itsthinning, the problem has become remarkable.

In view of the foregoing, in the production of a brittle film, such as aglass film, a possible method of preventing breakage during a process tosecure handleability is to protect the brittle film with a tough film.

CITATION LIST Patent Literature

[PTL 1] JP 4122139 B2

SUMMARY OF INVENTION Technical Problem

However, in the case where a brittle film, such as a glass film, isextremely thin, even when a tough film is bonded to the brittle film, aproblem in that the brittle film is broken occurs. In particular, whenthe brittle film is conveyed while having waviness resulting from aproduction process for the film or the like, at the time of the bonding,a pressure to be applied to the brittle film does not become constant,and hence the brittle film is liable to be easily broken.

The present invention has been made to solve the conventional problem,and an object of the present invention is to provide a production methodfor a film laminate by which a tough film can be bonded to a brittlefilm while the breakage of the brittle film is prevented.

Solution to Problem

According to one embodiment of the present invention, there is provideda production method for a film laminate, including bonding a tough filmhaving an elongated shape to a brittle film having an elongated shapewhile conveying the brittle film, wherein the method includes bondingthe tough film and the brittle film to each other by bringing the toughfilm close to the brittle film, followed by blowing of a gas from a sideof the tough film opposite to the brittle film.

In one embodiment, the brittle film has a thickness of from 20 μm to 300μm.

In one embodiment, a gas pressure at a time of the blowing of the gas isfrom 0.01 MPa to 1 MPa.

In one embodiment, the blowing of the gas is performed with a gasjetting apparatus including a gas jetting port, and a distance betweenthe gas jetting port and the brittle film is from 1 mm to 500 mm.

In one embodiment, a ratio of a width of the tough film to a width ofthe brittle film is from 1% to 110%.

In one embodiment, the tough film has an adhesive strength to thebrittle film of from 0.005 N/25 mm to 10 N/25 mm.

In one embodiment, the production method for a film laminate includesfeeding the tough film having an elongated shape, and applying anadhesive onto the tough film and/or the brittle film, followed bybonding of the tough film and the brittle film.

In one embodiment, the tough film is subjected as a tough film with anadhesion layer to the production method for a film laminate, and themethod includes feeding the tough film having an elongated shape, andapplying an adhesive onto the tough film to form the tough film with anadhesion layer, followed by continuous bonding of the tough film with anadhesion layer and the brittle film without take-up of the tough film.

In one embodiment, the blowing of the gas is performed on a support rollor a support base, the support roll or the support base being arrangedon a side of the brittle film opposite to the tough film.

Advantageous Effects of Invention

According to the present invention, the tough film can be bonded to thebrittle film while the breakage of the brittle film is prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view for illustrating a production method for afilm laminate according to one embodiment of the present invention.

FIG. 2 is a view for illustrating the waviness of a brittle film to besubjected to the production method for a film laminate according to oneembodiment of the present invention.

A production method for a film laminate of the present inventionincludes bonding a tough film having an elongated shape to a brittlefilm having an elongated shape while conveying the brittle film. Themethod of the present invention includes bonding the tough film and thebrittle film to each other by bringing the tough film close to thebrittle film, followed by blowing of a gas from a side of the tough filmopposite to the brittle film. That is, the present invention ischaracterized in that pressing means, such as a nip roll, is not used atthe time of the bonding of the brittle film and the tough film.

FIG. 1 is a schematic view for illustrating a production method for afilm laminate according to one embodiment of the present invention. Inthis embodiment, while a brittle film 10 having an elongated shape isconveyed, a tough film 20 is brought close to the brittle film 10 havingan elongated shape from above the brittle film 10, and a gas is blownfrom above the tough film 20. The tough film 20 having an elongatedshape is supplied so that the bonding of the brittle film 10 and thetough film 20 may be continuously performed. Although the brittle film10 is conveyed in a horizontal direction in the illustrated example, theconveying direction of the brittle film 10 is not particularly limited,and the conveying direction may be set to, for example, an obliquelyupward direction, an obliquely downward direction, a vertically upwarddirection, or a vertically downward direction. A method of conveying thebrittle film is, for example, roll conveyance or belt conveyance.

A film having a fracture toughness value of from 0.1 MPa/m^(1/2) to 10MPa/m^(1/2) may be used as the brittle film 10, and examples thereofinclude a glass film, a ceramic film, and a film formed of a brittlematerial, such as a semiconductor material or an acrylic resin. Afracture toughness value K_(Ic) is determined by: applying a tensilestress to an evaluation sample, which is obtained by making a crackhaving a length of 5 mm in an end portion (central portion) in thelengthwise direction of a brittle film having a predetermined size(measuring 2 cm wide by 15 cm long), in the lengthwise direction with anautograph (e.g., an autograph available under the product name “AG-I”from Shimadzu Corporation; chuck-to-chuck distance: 10 cm, tensile rate:10 mm/min); measuring a stress “σ” at the time of the rupture of thesample from the crack; and substituting the stress “σ”, a crack length“a”, and a sample width “b” into the following equation.

K _(IC)=σ(πa)^(1/2) F(a/b)

F(a/b)=1.12−0.231(a/b)+10.55(a/b)²−21.72(a/b)³+30.39(a/b)⁴

Typically, the brittle film 10 is a glass film. The glass film isproduced, for example, as follows: a mixture containing a main rawmaterial, such as silica or alumina, an antifoaming agent, such asmirabilite or antimony oxide, and a reducing agent, such as carbon, ismelted at a temperature of from 1,400° C. to 1,600° C., and formed intoa thin sheet shape, followed by cooling. A method of forming the glassfilm into a thin sheet is, for example, a slot down-draw method, afusion method, or a float method. In one embodiment, the brittle film 10(e.g., a glass film) formed into a thin sheet shape is subjected to theproduction method of the present invention as it is (i.e., without beingtaken up).

The thickness of the brittle film 10 is preferably 300 μm or less, morepreferably from 20 μm to 300 μm, still more preferably from 20 μm to 200μm, particularly preferably from 20 μm to 100 μm. In the presentinvention, even when an extremely thin brittle film (typically a glassfilm) is used, the breakage of the brittle film is prevented. The term“thickness of the brittle film” refers to the thickness of a portion towhich the tough film is bonded.

The width of the brittle film 10 is preferably from 50 mm to 2,000 mm,more preferably from 100 mm to 1,000 mm.

The length of the brittle film 10 is preferably 100 m or more, morepreferably 500 m or more. According to the present invention, a longbrittle film is supplied, and hence the brittle film and the tough filmcan be continuously bonded to each other without the breakage of thebrittle film.

In one embodiment, the brittle film 10 is conveyed while havingwaviness. In a conventional bonding method involving using pressingmeans, such as a nip roll, in the case where the brittle film isconveyed while having waviness, it is difficult to avoid the breakage ofthe brittle film at the time of its pressing. According to theproduction method of the present invention, however, even in such case,the brittle film and the tough film can be bonded to each other whilethe breakage of the brittle film is prevented. The phrase “conveyedwhile having waviness” as used herein refers to a state in which thebrittle film is conveyed in a wave shape as illustrated in FIG. 1 whenthe brittle film is viewed from a side.

The waviness occurs owing to, for example, a material forming thebrittle film and a production condition in a production process for thefilm, and its size is not particularly limited. When the waviness isrepresented by a radius of curvature R as illustrated in FIG. 2, theradius of curvature R is 0.3 mm or more in one embodiment, is 7 mm ormore in another embodiment, is 17 mm or more in still anotherembodiment, and is 34 mm or more in still another embodiment. The upperlimit of the radius of curvature R is, for example, 170 mm.

A film having a fracture toughness value larger than that of the brittlefilm may be used as the tough film 20. A film having a fracturetoughness value of, for example, from 2 MPa/m^(1/2) to 20 MPa/m^(1/2)may be used as the tough film 20, and for example, a film including anyappropriate tough material may be used. In one embodiment, a resin filmis used as the tough film 20. Examples of a resin forming the resin filminclude polyethylene, polyvinyl chloride, polyethylene terephthalate,polyvinylidene chloride, polypropylene, polyvinyl alcohol, polyester,polycarbonate, polystyrene, polyacrylonitrile, an ethylene-vinyl acetatecopolymer, an ethylene-vinyl alcohol copolymer, an ethylene-methacrylicacid copolymer, nylon, cellophane, and a silicone resin.

In one embodiment, the tough film is subjected as a tough film with anadhesion layer to the above-mentioned production method by beingprovided with an adhesion layer. Examples of a material forming theadhesion layer include an epoxy-based adhesive, a rubber-based adhesive,an acrylic adhesive, a silicone-based adhesive, and a urethane-basedadhesive. In addition, a resin having a cyclic ether group, such as anepoxy group, a glycidyl group, or an oxetanyl group, may be used as thematerial forming the adhesion layer. In addition, a curable adhesive maybe used. Herein, the adhesion layer is a concept including apressure-sensitive adhesion layer and the adhesive is a conceptincluding a pressure-sensitive adhesive.

In one embodiment, when the tough film with an adhesion layer is used,it is preferred that the tough film having an elongated shape be fed,and the adhesive be applied onto the tough film to form an adhesionlayer, followed by continuous bonding of the tough film with an adhesionlayer (laminate of the tough film and the adhesion layer) and thebrittle film without the take-up of the tough film.

In another embodiment, after the tough film having an elongated shape(e.g., a tough film free of any adhesion layer) has been fed, and beforethe tough film and the brittle film are bonded to each other, theadhesive is applied onto the tough film and/or the brittle film.

As a method of applying the adhesive, there are given: coating methods,e.g., air doctor coating, blade coating, knife coating, reverse coating,transfer roll coating, gravure roll coating, kiss coating, cast coating,spray coating, slot orifice coating, calender coating, electrocoating,dip coating, and die coating; and printing methods, e.g., reliefprinting methods, such as flexographic printing, intaglio printingmethods, such as a direct gravure printing method and an offset gravureprinting method, litho printing methods, such as an offset printingmethod, and stencil printing methods, such as a screen printing method.When a curable adhesive is used, the adhesion layer may be cured afterthe tough film and the brittle film have been bonded to each other. Amethod for the curing is, for example, a method involving curing theadhesive through ultraviolet light irradiation and/or heat treatment. Anirradiation condition for the ultraviolet light irradiation is typicallyas follows: a cumulative irradiation light amount is from 100 mJ/cm² to2,000 mJ/cm², preferably from 200 mJ/cm² to 1,000 mJ/cm².

The adhesive strength of the tough film 20 to the brittle film 10 ispreferably from 0.005 N/25 mm to 10 N/25 mm. The adhesive strength ofthe tough film may be adjusted by, for example, the material forming theadhesion layer. In one embodiment, when the tough film 20 needs to bere-peeled, the adhesive strength of the tough film 20 to the brittlefilm 10 is preferably from 0.005 N/25 mm to 1.0 N/25 mm, more preferablyfrom 0.05 N/25 mm to 0.9 N/25 mm. The adhesive strength may be measuredwith a pressure-sensitive adhesive strength-measuring apparatus (e.g.,an Instron-type tensile tester, manufactured by Shimadzu Corporation,AUTOGRAPH) under the conditions of a temperature of 23° C., a humidityof 50% RH, a peeling direction of 180°, and a peel rate of 300 mm/minafter the lapse of 30 minutes from the bonding of the tough film to thebrittle film.

The thickness of the tough film 20 is preferably from 3 μm to 250 μm,more preferably from 5 μm to 250 μm, still more preferably from 20 μm to150 μm. When the tough film includes a base material and an adhesionlayer, the thickness of the base material is preferably from 2 μm to 200μm, more preferably from 10 μm to 100 μm, and the thickness of theadhesion layer is preferably from 1 μm to 50 μm, more preferably from 5μm to 30 μm.

The ratio of the width of the tough film 20 to the width of the brittlefilm 10 is from 1% to 110%. The width of the tough film is set to anyappropriate width in accordance with the purpose of the bonding of thetough film. For example, when it is intended to reinforce an end portionin the widthwise direction of the brittle film, the ratio of the widthof the tough film to the width of the brittle film is preferably from 1%to 20%, more preferably from 2% to 15%. In addition, when the entiresurface of the brittle film is reinforced, the ratio of the width of thetough film to the width of the brittle film is preferably from 80% to110%, more preferably from 90% to 100%.

The length of the tough film 20 may be set to any appropriate length inaccordance with the length of the brittle film 10.

The blowing of the gas is performed at a time point when the brittlefilm 10 and the tough film 20 are sufficiently close to each other. Thegas may be blown before the brittle film 10 and the tough film 20 arebrought into contact with each other, or the gas may be blown after thebrittle film 10 and the tough film 20 have been brought into contactwith each other. When the gas is blown before the brittle film 10 andthe tough film 20 are brought into contact with each other, the blowingof the gas is performed at a site where a distance between the brittlefilm 10 and the tough film 20 (a distance before the blowing of the gasor a distance when the gas is not blown) is, for example, more than 0 mmand 100 mm or less (preferably more than 0 mm and 50 mm or less, morepreferably more than 0 mm and 20 mm or less). The brittle film 10 andthe tough film 20 are brought into contact with each other by theblowing of the gas, and hence the bonding of the brittle film 10 and thetough film 20 is completed.

In one embodiment, a support roll or a support base is arranged on theside of the brittle film 10 opposite to the tough film 20, and theblowing of the gas is performed on the support roll or the support base.With such procedure, the brittle film and the tough film can besatisfactorily bonded to each other without, for example, the inclusionof air bubbles. In FIG. 1, an example in which a support roll 30 isarranged on the side of the brittle film 10 opposite to the tough film20 (i.e., below the brittle film 10) is illustrated.

The blowing of the gas may be performed with any appropriate gas jettingapparatus 40. In one embodiment, with a view to blowing the gas to theentire width of the tough film to be bonded, for example, a gas jettingapparatus including a plurality of gas jetting ports arrayed in itswidthwise direction is used. In another embodiment, with a view toblowing the gas to a part (e.g., a central portion) in the widthwisedirection of the tough film to be bonded, for example, a gas jettingapparatus including a plurality of gas jetting ports arrayed in itslengthwise direction is used. Such form is effective when the adhesiveis applied to a part (e.g., a central portion) in the widthwisedirection of the brittle film or the tough film, and the adhesive can bespread by blowing the gas to a site having applied thereto the adhesive.In addition, a gas jetting apparatus including a plurality of gasjetting ports arrayed in its widthwise direction and lengthwisedirection may be used.

A gas pressure at the time of the blowing of the gas is preferably from0.01 MPa to 1 MPa, more preferably from 0.05 MPa to 0.8 MPa, still morepreferably from 0.1 MPa to 0.6 MPa. When the gas pressure falls withinsuch range, the brittle film and the tough film can be satisfactorilybonded to each other while the occurrence of, for example, a wrinkle andair bubbles is suppressed.

A distance between the brittle film 10 and a gas jetting port 31 at thetime of the blowing of the gas is preferably from 1 mm to 500 mm, morepreferably from 1.5 mm to 100 mm, still more preferably from 2 mm to 50mm. When the distance falls within such range, the brittle film and thetough film can be satisfactorily bonded to each other while theoccurrence of, for example, a wrinkle and air bubbles is suppressed.

In one embodiment, as in the illustrated example, the jetting directionof the gas is substantially perpendicular to the plane (morespecifically, the tangent plane at the collision position of the gas) ofthe brittle film 10. In this embodiment, the jetting angle of the gaswith respect to the plane (tangent plane) of the brittle film 10 ispreferably from 75° to 105°, more preferably from 80° to 100°, stillmore preferably from 85° to 95° in the conveying direction of thebrittle film 10. In another embodiment, the jetting direction of the gasis an oblique direction with respect to the plane (tangent plane) of thebrittle film 10. In this embodiment, the jetting angle of the gas withrespect to the plane (tangent plane) of the brittle film 10 ispreferably 30° or more and less than 75°, or more than 105° and 150° orless, more preferably from 45° to 70° or from 110° to 135° in theconveying direction of the brittle film 10. The angle as used hereinrefers to an angle determined by defining a counterclockwise directionwith reference to the plane (tangent plane) direction of the brittlefilm when viewed from a side of the brittle film during its conveyanceas a positive (+) direction. Therefore, the jetting of the gas at anangle of less than 90° (absolute value) with respect to the plane(tangent plane) direction of the brittle film corresponds to the jettingof the gas from a downstream side in the conveying direction of thebrittle film toward an upstream side therein.

According to the present invention, the bonding of the brittle film andthe tough film is completed as described above, and hence a laminate ofthe brittle film and the tough film can be obtained. According to theproduction method of the present invention, the tough film can besatisfactorily bonded to the brittle film while a load to be applied tothe brittle film is extremely small. In one embodiment, the laminate ofthe brittle film and the tough film may be taken up in a roll shape. Inanother embodiment, the tough film is bonded for temporal protection ofthe brittle film (e.g., the protection of a slit portion at the time ofthe slitting of an end portion of the brittle film), and then the toughfilm is peeled before the take-up of the brittle film. In addition, inthe production of the laminate of the brittle film and the tough film, alaminate including the tough film on each of both surfaces of thebrittle film may be produced by using the above-mentioned bonding methodtwice.

EXAMPLES

Now, the present invention is specifically described by way of Examples.However, the present invention is by no means limited to these examples.

Example 1

While a glass film having an elongated shape (thickness: 100 μm, width:500 mm, fracture toughness value: 0.7 MPa/m^(1/2)) was conveyed in ahorizontal direction on a support roll, the adhesion layer side of atough film with an adhesion layer was brought close to, and into contactwith, the glass film from above the glass film, and a gas was blown fromabove the tough film with an adhesion layer (tough film side) at thecontact point. The tough film with an adhesion layer includes a toughfilm formed of PET (thickness: 100 μm, width: 25 mm, fracture toughnessvalue: 3 MPa/m^(1/2)) and an adhesion layer (thickness: 5 μm). Theadhesion layer was formed by applying an epoxy-based adhesive to thetough film immediately before the glass film and the tough film werebrought into contact with each other. In addition, a gas pressure wasset to 0.4 MPa, and a distance between a gas jetting port and the glassfilm was set to 3 mm. The glass film was conveyed while having wavinesshaving a radius of curvature R of 3 mm.

In this example, the glass film and the tough film having a length of500 m or more were able to be continuously bonded to each other withoutthe breakage of the glass film.

Comparative Example 1

The same glass film and tough film as those of Example 1 were used, andthe films were bonded to each other between a pair of rolls (between asupport roll and a nip roll). The rubber hardness of the nip roll wasset to 70°, and a linear pressure to be applied between the rolls wasset to 2,000 N.

In this comparative example, the breakage of the thin glass occurred,and hence the glass film and the tough film could not be satisfactorilybonded to each other.

INDUSTRIAL APPLICABILITY

The production method of the present invention can be suitably used as asubstrate for a display element, a sealing material of an OLED element,a front protective sheet, or the like.

REFERENCE SIGNS LIST

-   10 brittle film-   20 tough film

1. A production method for a film laminate, comprising bonding a toughfilm having an elongated shape to a brittle film having an elongatedshape while conveying the brittle film, wherein the method comprisesbonding the tough film and the brittle film to each other by bringingthe tough film close to the brittle film, followed by blowing of a gasfrom a side of the tough film opposite to the brittle film.
 2. Theproduction method for a film laminate according to claim 1, wherein thebrittle film has a thickness of from 20 μm to 300 μm.
 3. The productionmethod for a film laminate according to claim 1, wherein a gas pressureat a time of the blowing of the gas is from 0.01 MPa to 1 MPa.
 4. Theproduction method for a film laminate according to claim 1, wherein theblowing of the gas is performed with a gas jetting apparatus including agas jetting port, and wherein a distance between the gas jetting portand the brittle film is from 1 mm to 500 mm.
 5. The production methodfor a film laminate according to claim 1, wherein a ratio of a width ofthe tough film to a width of the brittle film is from 1% to 110%.
 6. Theproduction method for a film laminate according to claim 1, wherein thetough film has an adhesive strength to the brittle film of from 0.005N/25 mm to 10 N/25 mm.
 7. The production method for a film laminateaccording to claim 1, wherein the method comprises feeding the toughfilm having an elongated shape, and applying an adhesive onto the toughfilm and/or the brittle film, followed by bonding of the tough film andthe brittle film.
 8. The production method for a film laminate accordingto claim 1, wherein the tough film is subjected as a tough film with anadhesion layer to the production method for a film laminate, and whereinthe method comprises feeding the tough film having an elongated shape,and applying an adhesive onto the tough film to form the tough film withan adhesion layer, followed by continuous bonding of the tough film withan adhesion layer and the brittle film without take-up of the toughfilm.
 9. The production method for a film laminate according to claim 1,wherein the blowing of the gas is performed on a support roll or asupport base, the support roll or the support base being arranged on aside of the brittle film opposite to the tough film.